Combining the specificity of a monoclonal antibody with the cell killing ability of a cytotoxic agent is an outstanding method for treating cancer. There are three components to this strategy; the antibody, linker , and cytotoxic drug. Assembling the correct combination of these components is key to the success of this method. These variables can be used in concert to widen the therapeutic window of cytotoxic drugs. This presentation will briefly review some of the successful applications of this technology and discuss in more depth the future directions of the linkers and cytotoxic drugs used in this approach.